Various proposals have been made conventionally to realize a high-velocity autofocus (AF) operation. For example, Japanese Patent Laid-Open No. 2002-72074 discloses a technique of speeding up autofocus control processing by determining the lens operation direction in focus control in accordance with the image sensing situation.
In this autofocus control processing, an AF search operation is performed in which while moving the focus lens during the shutter button being pressed halfway, image signals are obtained from the CCD at different positions, and an evaluation value is obtained on the basis of the contrast components of the acquired image signals. At this time, the focus position and zoom position are detected at the start of AF search operation. If the current focus position is located on the short distance side in the focus detection area, the direction from the closest distance to the infinite distance is determined as the search direction. On the other hand, if the current focus position is located on the long distance side in the focus detection area, the direction from the infinite distance to the closest distance is determined as the search direction. In addition, if the current zoom position is located on the wide-angle side, the search direction is set from the closest distance to the infinite distance. If the current zoom position is located on the telephoto side, the search direction is set from the infinite distance to the closest distance.
In the above-described prior art, the search direction is determined on the basis of the focus position and zoom position at the start of AF search operation. For this reason, search may be started from the closest distance side even when the object exists on the long distance side at a high probability.
Additionally, search is started always from the closest end or infinite end. Hence, when the object exists near the focus position at the start of AF search operation, focus lens movement and search operation are done needlessly, hindering speed-up of autofocus control processing.